Cleanup wrong epoch messages on creating new group

[insipx]

• One way make it less noisy is just not to show them
  • If epoch is smaller than current epoch, not a big deal that cannot decrypt because message came before joined
  • If bigger might have some issues
    • Can’t decrypt new messages
• When join tell someone in group at what point to start syncing
• Another thing to do is to have a flag when added to group, and check is up to date true/false (has synced true/false)
  • Throw away epoch errors while false until have non-error message and set to true from that point on